1. Field of the Invention
The present invention relates to an apparatus for anchoring surgical suture to bone. More specifically, the present invention relates to a suture anchor having an internal suture loop for receiving one or more strands of suture to anchor the suture to bone during arthroscopic surgery.
2. Description of the Related Art
When soft tissue tears away from bone, reattachment becomes necessary. Various devices, including sutures alone, screws, staples, wedges, and plugs have been used in the prior art to secure soft tissue to bone.
Recently, various types of threaded suture anchors have been developed for this purpose. Some threaded suture anchors are designed to be inserted into a pre-drilled hole. Other suture anchors are self-tapping.
U.S. Pat. No. 4,632,100 discloses a cylindrical threaded suture anchor. The suture anchor of the ""100 patent includes a drill bit at a leading end for boring a hole in a bone, followed by a flight of threads spaced from the drill bit for securing the anchor into the hole created by the drill bit.
U.S. Pat. No. 5,370,662 discloses a suture anchor having threads which extend to the tip of the anchor. U.S. Pat. No. 5,156,616 discloses a similar suture anchor having an axial opening for holding a knotted piece of suture.
All of the above-noted suture anchors include structure for attaching the suture to the anchor. U.S. Pat. No. 4,632,100, for example, discloses a press-fitted disc and knot structure which secures the suture to the anchor. In other suture anchors, such as those disclosed in U.S. Pat. No. 5,370,662, the suture is passed through an eyelet located on the proximal end of the anchor. In the case of a bioabsorbable suture anchor, the suture may be insert molded into the anchor, as disclosed in U.S. Patent No. 5,964,783.
Problems can arise if the structure for attaching the suture fails, allowing the suture to become detached from the anchor. Also, the suture often is exposed to abrasion or cutting by sharp or rough areas along the walls of the bone canal into which the anchor is inserted.
Moreover, the eyelet or, in the case of U.S. Pat. No. 4,632,100, the axial opening for receiving the disc to which the suture is knotted, is formed as part of the drive head of the known suture anchors. Combining these two functions in one structure often tends to weaken the drive head.
In addition, various other modifications to the drive head often are employed in connection with suture attachment. For example, recessed grooves may be formed on opposite sides of the drive head to receive and protect the suture from abrasive areas of the suture anchor tunnel or to facilitate mating between the anchor to the driver. In such cases, the drive head often must be made of a larger diameter to recover the mechanical strength lost from the removal of material relating to the suture-attachment or suture-protection modifications.
Further, the prior art suture anchors having eyelets extending from the proximal ends require countersinking of the eyelet below the bone surface to avoid having the patient""s tissue abrade against the exposed eyelet. As a result, suture attached to the eyelet is vulnerable to abrasion by the bony rim of the countersunk hole into which the suture anchor is installed. In addition, in biodegradable suture anchors, the suture eyelet can degrade rapidly, causing the suture to become detached from the anchor prematurely.
Accordingly, there is a need for a threaded suture anchor to which suture is secured effectively so as to prevent detachment of the suture. It is further desirable for such suture anchors to have eyelets that will not abrade tissue and which do not require countersinking.
The suture anchor of the present invention overcomes the disadvantages of the prior art discussed above by providing a threaded suture anchor having a suture loop disposed inside the body of the suture anchor. The suture anchor is made of a biocompatible metal, preferably a titanium alloy.
The proximal end surface of the threaded suture anchor of the present invention is preferably smooth and rounded to minimize suture abrasion, while the distal portion of the anchor is tapered to an elongated point to enable the anchor to be self-tapping. The proximal end portion of the suture anchor body has a hexagonally shaped opening to accept a hexagonal drive head.
The internal suture loop extends through a substantial length of the anchor body with the ends of the suture loop secured onto the distal end portion of the anchor and the proximal end of the loop being flush with or recessed just below the plane across the proximal face of the anchor.
Advantageously, suture attached to the anchor through the suture loop exits the suture anchor through a central bore in the anchor, which prevents suture abrasion by the wall of the bone tunnel into which the anchor is inserted.
Other features and advantages of the present invention will become apparent from the following description of the invention, which refers to the accompanying drawings.